Medical Imaging

We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast-enhanced T 1 -weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd-DTPA). These include a) the volume transfer constant K trans (min ؊1 ); b) the volume of extravascular extracellular space (EES) per unit volume of tissue v e (0 F v e F 1); and c) the flux rate constant between EES and plasma k ep (min ؊1 ). The rate constant is the ratio of the transfer constant to the EES (k ep ‫؍‬ K trans / v e ). Under flow-limited conditions K trans equals the blood plasma flow per unit volume of tissue; under permeability-limited conditions K trans equals the permeability surface area product per unit volume of tissue. We relate these quantities to previously published work from our groups; our future publications will refer to these standardized terms, and we propose that these be adopted as international standards.

The types I, II, and III receptors (RI, RII, RIII) for transforming growth factor-␤ (TGF-␤) become downregulated in response to ligand, presumably via their internalization from the cell surface. This report examines the down-regulation of full-length RI, RII, and RIII in cells endogenously or transiently expressing these receptors. Down-regulation occurred rapidly (within 2 h after TGF-␤1 treatment at 37°C) and showed a dose response, between 10 and 200 pM TGF-␤1, in cells expressing RI, RII, and RIII (Mv1lu and A549 cells). A comparison between Mv1Lu and mutant cell derivatives R-1B (lacking RI) or DR-26 (lacking RII) indicated that all three receptors were necessary for efficient down-regulation. Down-regulation experiments, utilizing TGF-␤-treated 293 cells transiently expressing different combinations of these receptors indicated that neither RII or RIII were down-regulated when expressed alone and that RI was required for maximal down-regulation of RII. RII and RIII were partially down-regulated when these receptors were coexpressed in the absence of RI (in R-1B and 293 cells). Surprisingly, TGF-␤ receptors were partially down-regulated in Mv1Lu, A549, and 293 cells treated with TGF-␤1 at 4°C. Microscopic examination of 293 cells coexpressing RI fused to green fluorescent protein (RI-GFP) and RII indicated that, after treatment with TGF-␤1 at 4°C, RI-GFP formed aggregates at the cell surface at this temperature. RI-GFP was not detected at the surface of these cells after TGF-␤1 treatment at 37°C. Our results suggest a two phase mechanism for TGF-␤1 receptor down-regulation involving receptor modulation (aggregation) at the cell surface and internalization.

Prostatic adenocarcinoma is one of the most commonly occurring cancers among men in the world, and it also the most curable cancer when it is detected early. Multiparametric MRI (mpMRI) combines anatomic and functional prostate imaging techniques, which have been shown to produce high sensitivity and specificity in cancer localization, which is important in planning biopsies and focal therapies. However, in previous investigations, lesion localization was achieved mainly by manual segmentation, which is time-consuming and prone to observer variability. Here, we developed an algorithm based on locality alignment discriminant analysis (LADA) technique, which can be considered as a version of linear discriminant analysis (LDA) localized to patches in the feature space. Sensitivity, specificity and accuracy generated by the proposed algorithm in five prostates by LADA were 52.2%, 89.1% and 85.1% respectively, compared to 31.3%, 85.3% and 80.9% generated by LDA. The delineation accuracy attainable by this tool has a potential in increasing the cancer detection rate in biopsies and in minimizing collateral damage of surrounding tissues in focal therapies.

There is little known about the impact of nonalcoholic fatty liver disease (NAFLD) on drug metabolism and transport. We examined the pharmacokinetics of oral apixaban (2.5 mg) and rosuvastatin (5 mg) when administered simultaneously in subjects with magnetic resonance imaging-confirmed NAFLD ( = 22) and healthy control subjects ( = 12). The area under the concentration-time curve to the last sampling time (AUC) values for apixaban were not different between control and NAFLD subjects (671 and 545 ng/ml × hour, respectively; = 0.15). Similarly, the AUC values for rosuvastatin did not differ between the control and NAFLD groups (25.4 and 20.1 ng/ml × hour, respectively; = 0.28). Furthermore, hepatic fibrosis in NAFLD subjects was not associated with differences in apixaban or rosuvastatin pharmacokinetics. Decreased systemic exposures for both apixaban and rosuvastatin were associated with increased body weight ( < 0.001 and < 0.05, respectively). In multivariable linear regress...

We observed a 45% decrease in mean PSA at 12 months post therapy and no statistically significant change in IPSS and SHIM scores. CONCLUSIONS: Our data indicate that outpatient, transrectally delivered MRI-guided laser focal therapy for prostate cancer is both safe and feasible. In the current climate of cost-reduction and emphasis on minimally-invasive treatment of cancer, focal treatment of prostate cancer may be an attractive option. The precision and controllability achieved under MRI-guidance may have favorable results for cost effectiveness and quality of life without eliminating the possibility of whole-gland treatment in the future. We will continue to follow these men for twenty years as part of an IRB-approved clinical trial (NCT# 02243033)[3].

The Liver Imaging Reporting and Data System (LI-RADS ®) is a comprehensive system for standardizing the terminology, technique, interpretation, reporting, and data collection of liver observations in individuals at high risk for hepatocellular carcinoma (HCC). LI-RADS is supported and endorsed by the American College of Radiology (ACR). Upon its initial release in 2011, LI-RADS applied only to liver observations identified at CT or MRI. It has since been refined and expanded over multiple updates to now also address ultrasound-based surveillance, contrast-enhanced ultrasound for HCC diagnosis, and CT/MRI for assessing treatment response after locoregional therapy. The LI-RADS 2018 version was integrated into the HCC diagnosis, staging, and management practice guidance of the American Association for the Study of Liver Diseases (AASLD). This article reviews the major LI-RADS updates since its 2011 inception and provides an overview of the currently published LI-RADS algorithms.

Background: Bone conduction implants can be used in the treatment of conductive or mixed hearing loss. The BONEBRIDGE bone conduction implant (BB-BCI) is an active, transcutaneous device. BB-BCI implantation can be performed through either the transmastoid or retrosigmoid approach with their respective limitations. Here, we present a third, novel approach for BB-BCI implantation. Objective: Describe the detailed surgical technique of BB-BCI implantation through a middle fossa approach with self-drilling screws and present preliminary audiometric outcome data following this approach. Methods: A single institution, retrospective chart review was completed for patients implanted with the BB-BCI via the middle fossa approach. Preoperative planning and modelling were performed using 3D Slicer. Audiological testing was performed pre-and post-operatively following standard audiometric techniques. Results: Forty patients underwent BB-BCI implantation using the middle fossa approach. Modelling techniques allowed for implantation through the use of external landmarks, obviating the need for intraoperative image guidance. The surgical technique was refined over time through experience and adaptation. Mean follow-up was 29 months (range 3-71 months) with no surgical complications, favourable cosmesis, and expected audiometric outcomes. An average functional gain of 39.6 dB (± 14.7 SD) was found. Conclusion: The middle fossa technique with self-drilling screws is a safe and effective option for BONEBRIDGE implantation. As a reference for other groups considering this approach, an annotated video has been included as a supplement to the study.

Introduction: Differentiation of renal cell carcinoma (RCC) from oncocytoma is a common diagnostic dilemma. A few studies have shown that 99mTc-sestamibi (MIBI) imaging has the potential to characterize indeterminate renal masses. This comparative study evaluated the utility of MIBI single-photon emission computed tomography-computed tomography (SPECT-CT) in the assessment and risk stratification of renal masses. Methods: A total of 29 patients with 31 renal masses who had cross-sectional imaging and MIBI SPECT-CT, were included. Lesions were categorized as either MIBI-positive or -negative on SPECT-CT. Individual lesion density ranged from 22–56 Hounsfield Units (HU) on the non-contrast CT part of SPECT-CT. Quantitative relative MIBI uptake was calculated by measuring tumor to ipsilateral renal parenchymal uptake. The imaging results were correlated with histopathology. Results: All oncocytic lesions, including seven oncocytomas and one hybrid oncocytic chromophobe tumor (100%), we...

BACKGROUND The Anatomy and Radiology Contouring (ARC) Bootcamp was a face-to-face (F2F) course designed to ensure radiation oncology residents were equipped with the knowledge and skillset to use radiation therapy techniques properly. The ARC Bootcamp was proven to be a useful educational intervention for improving learners’ knowledge of anatomy and radiology and contouring ability. An online version of the course was created to increase accessibility to the ARC Bootcamp and provide a flexible, self-paced learning environment. This study aimed to describe the instructional design model used to create the online offering and report participants’ motivation to enroll in the course and the online ARC Bootcamp's strengths and improvement areas. METHODS The creation of the online course followed the analysis, design, development, implementation, and evaluation (ADDIE) framework. The course was structured in a linear progression of locked modules consisting of radiology and contouring...

Multiparametric MRI (mpMRI) has shown promise in the detection and localization of prostate cancer foci. Although techniques have been previously introduced to delineate lesions from mpMRI, these techniques were evaluated in data sets with T2 maps available. The generation of T2 map is not included in the clinical prostate mpMRI consensus guidelines; the acquisition of which requires repeated T2-weighted (T2W) scans and would significantly lengthen the scan time currently required for the clinically recommended acquisition protocol, which includes T2W, diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) imaging. The goal of this study is to develop and evaluate an algorithm that provides pixel-accurate lesion delineation from images acquired based on the clinical protocol. 25 pixel-based features were extracted from the T2-weighted (T2W), apparent diffusion coefficient (ADC) and dynamic contrast-enhanced (DCE) images. The pixel-wise classifi-cation was performed on the reduc...

To report the 3‐year follow‐up of a Phase I study of magnetic resonance imaging (MRI)‐guided transurethral ultrasound ablation (TULSA) in 30 men with localised prostate cancer. Favourable 12‐month safety and ablation precision were previously described.

fit an elastic-net penalized Cox regression model with these 242 features, which was applied to all patients. The Cox model output a risk score for each patient. This process was termed "Histotyping". The concordance index (c-index) of Histotyping and Decipher in BCRfree survival were compared. RESULTS: The nine features selected by the Cox model included seven measures of average lumen shape and variation of lumen shape, one feature of lumen arrangement, and one feature of image texture. A greater variation across the tumor in lumen shape and density and a less smooth image texture were associated with increased BCR risk. Histotyping performed comparably to Decipher (cindex 0.66 vs. 0.70) in BCR prognosis. CONCLUSIONS: Computerized visual analysis of a routinely acquired H&E slides was found to perform comparably to Decipher in BCR prognosis. A limitation of this work is that Decipher is optimized for metastasis prognosis, though metastasis outcome information was not available for these patients.

Multiparametric magnetic resonance imaging (mpMRI) has been established as the state-of-the-art examination for the detection and localization of prostate cancer lesions. Prostate Imaging-Reporting and Data System (PI-RADS) has been established as a scheme to standardize the reporting of mpMRI findings. Although lesion delineation and PI-RADS ratings could be performed manually, human delineation and ratings are subjective and time-consuming. In this article, we developed and validated a self-tuned graph-based model for PI-RADS rating prediction. 34 features were obtained at the pixel level from T2-weighted (T2W), apparent diffusion coefficient (ADC) and dynamic contrast enhanced (DCE) images, from which PI-RADS scores were predicted. Two major innovations were involved in this self-tuned graph-based model. First, graph-based approaches are sensitive to the choice of the edge weight. The proposed model tuned the edge weights automatically based on the structure of the data, thereby ...

Combined PET/MRI is a proposed imaging modality for rectal cancer, leveraging the advantages of MRI and 18F-fluorodeoxyglycose PET. Rectal cancer PET/MRI protocols typically include dedicated pelvis bed positions utilizing small field of view T2 weighted imaging. For staging of the primary tumor, PET/MRI can help delineate the extent of tumor better as well as the extent of tumor beyond the muscularis propria. PET uptake may help characterize small lymph nodes, and the use of hepatobiliary phase imaging can improve the detection of small hepatic metastases. The most beneficial aspect of PET/MRI may be in treatment response, although current data is limited on how to combine PET and MRI data in this setting. Limitations of PET/MRI include the inability to detect small pulmonary nodules and issues related to attenuation correction, although the development of new attenuation correction techniques may address this issue. Overall PET/ MRI, has can improve the staging of rectal cancer although this potential has yet to be fulfilled.

The Society of Abdominal Radiology’s Colorectal and Anal Cancer Disease-Focused Panel (DFP) first published a rectal cancer lexicon paper in 2019. Since that time, the DFP has published revised initial staging and restaging reporting templates, and a new SAR user guide to accompany the rectal MRI synoptic report (primary staging). This lexicon update summarizes interval developments, while conforming to the original lexicon 2019 format. Emphasis is placed on primary staging, treatment response, anatomic terminology, nodal staging, and the utility of specific sequences in the MRI protocol. A discussion of primary tumor staging reviews updates on tumor morphology and its clinical significance, T1 and T3 subclassifications and their clinical implications, T4a and T4b imaging findings/definitions, terminology updates on the use of MRF over CRM, and the conundrum of the external sphincter. A parallel section on treatment response reviews the clinical significance of near-complete respons...

BACKGROUND: The Anatomy and Radiology Contouring (ARC) Bootcamp was a face-to-face (F2F) course designed to ensure radiation oncology residents were equipped with the knowledge and skillset to use radiation therapy techniques properly. The ARC Bootcamp was proven to be a useful educational intervention for improving learners' knowledge of anatomy and radiology and contouring ability. An online version of the course was created to increase accessibility to the ARC Bootcamp and provide a flexible, self-paced learning environment. This study aimed to describe the instructional design model used to create the online offering and report participants' motivation to enroll in the course and the online ARC Bootcamp's strengths and improvement areas. METHODS: The creation of the online course followed the analysis, design, development, implementation, and evaluation (ADDIE) framework. The course was structured in a linear progression of locked modules consisting of radiology and contouring lectures, anatomy labs, and integrated evaluations. RESULTS: The online course launched on the platform Teachable in November 2019, and by January 2021, 140 participants had enrolled in the course, with 27 participants completing all course components. The course had broad geographic participation with learners from 19 different countries. Of the participants enrolled, 34% were female, and most were radiation oncology residents (56%), followed by other programs (24%), such as medical physics residents or medical students. The primary motivator for participants to enroll was to improve their subject knowledge/skill (44%). The most common strength identified by participants was the course's quality (41%), and the most common improvement area was to incorporate more course content (41%). CONCLUSIONS: The creation of the online ARC Bootcamp using the ADDIE framework was feasible. The course is accessible to diverse geographic regions and programs and provides a flexible learning environment; however, the course completion rate was low. Participants' feedback regarding their experiences will inform future offerings of the online course.

Advances in imaging have changed prostate radiotherapy through improved biochemical control from focal boost and improved detection of recurrence. These advances are reviewed in the context of prostate stereotactic body radiation therapy (SBRT) and the ARGOS/CLIMBER trial protocol. ARGOS/CLIMBER will evaluate 1) the safety and feasibility of SBRT with focal boost guided by multiparametric MRI (mpMRI) and 18F-PSMA-1007 PET and 2) imaging and laboratory biomarkers for response to SBRT. To date, response to prostate SBRT is most commonly evaluated using the Phoenix Criteria for biochemical failure. The drawbacks of this approach include lack of lesion identification, a high false-positive rate, and delay in identifying treatment failure. Patients in ARGOS/CLIMBER will receive dynamic 18F-PSMA-1007 PET and mpMRI prior to SBRT for treatment planning and at 6 and 24 months after SBRT to assess response. Imaging findings will be correlated with prostate-specific antigen (PSA) and biopsy re...

Background: Non-alcoholic fatty liver disease (NAFLD) has become a pandemic, affecting up to 25% of the global population, with high incidence and prevalence in North America. 1 The spectrum of disease ranges from simple steatosis to steatohepatitis, with or without fibrosis (NASH). It is important to be able to diagnose patients with simple steatosis, but even more so to identify those with NASH given their increased risk of progression to cirrhosis. The gold standard for NASH diagnosis remains liver biopsy. However, given its invasive nature and recognized sampling error from heterogeneity of disease distribution, there has been an increase in the use of non-invasive techniques. 2 MRI-fat fraction (MR-FF) is validated for the assessment of hepatic steatosis 3 and MR elastography (MRE) for fibrosis. 4 MRE requires special hardware and software not readily available. As such, a more readily available imaging modality known as gadoxetic-acid enhanced MRI (GE-MRI), has shown to potentially differentiate simple steatosis from NASH. 5 Aims: To determine if GE-MRI can differentiate NAFLD from healthy controls compared to MR-FF, and/or simple steatosis from NASH compared to MRE. Methods: Healthy controls and NAFLD patients provided informed written consent to participate in this cross-sectional cohort study. The study was approved by the Research Ethics Board at Western University. The diagnosis of NAFLD was based on the AASLD definition. 6 These NAFLD patients were divided into those with simple steatosis or NASH based on liver biopsy or transient elastography. All patients underwent MRI-FF, MRE, and GE-MRI. Results: A total of 17 patients were studied. Five healthy control and 12 NAFLD patients, of whom 3 had biopsy proven NASH and 4 had fibrosis based on transient elastography, the remaining 5 had simple steatosis. GE-MRI was able to differentiate healthy patients from NAFLD patients [mean enhancement difference-35.07 ± 11.66 (p=0.0088)]. MR-FF had a statistically significant difference [0.2823 ± 0.03726 (p<0.0001)] and differentiated all patients with NAFLD. GE-MRI was not able to differentiate between hepatic steatosis and NASH, but there was a mean difference in enhancement of 18.67. MRE was able to differentiate between all patients with simple steatosis and NASH with statistical significance [mean difference-1.799 (95% CI =